Eating fatty, sugar-laden foods causes chemical changes in the brain — similar to what happens with drug addicts — that can cause withdrawal-like symptoms and even depression in people who suddenly switch to healthier diets.
That’s the key finding of a new study by University of Montreal food scientists that may explain why it’s difficult for so many people to give up high-fat, high-sugar diets, even though they know they should. Although the research involved lab studies of mice, the findings have significant implications for people, said lead researcher Stephanie Fulton, M.D., of the University of Montreal's Faculty of Medicine and its affiliated CRCHUM Hospital Research Centre.
"By working with mice, whose brains are in many ways comparable to our own, we discovered that the neurochemistry of the animals who had been fed a high-fat, sugary diet were different from those who had been fed a healthy diet," Dr. Fulton explained. "The chemicals changed by the diet are associated with depression. A change of diet then causes withdrawal symptoms and a greater sensitivity to stressful situations, launching a vicious cycle of poor eating."
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Even before obesity occurs, eating junk foods causes chemical changes in the brain, said the researchers who compared mice fed a low-fat diet with those on a high-fat diet over six weeks. Over the course of the study, investigators monitored the mice’s behavior and examined their brains for changes.
The results showed mice fed higher-fat diets were more anxious and their brains underwent substantive changes that led to more production of dopamine — a chemical tied to positive feelings and the pleasure centers of the brains of mice and humans alike. They also had higher levels of the stress hormone corticosterone.
“This explains both the depression and the negative behavior cycle," Dr. Fulton said. "It's interesting that these changes occur before obesity. These findings challenge our understanding of the relationship between diet, the body, and the mind. It is food for thought about how we might support people psychologically as they strive to adopt healthy eating habits, regardless of their current corpulence."
The study, published online in the International Journal of Obesity, was funded by the Natural Sciences and Engineering Research Council of Canada, the Canadian Diabetes Association, and the Canada Foundation for Innovation.